Ideas and principles

The NOWAC study has been founded on ideas related to what could be called natural or comparative advantages for internationally competitive epidemiological cancer research in Norway.

An unique national opportunity for a representative prospective study based on sampling from the national population register of Norway with adequate external validity for comparing relative risks with population attributable risk as an important aspect of public health priorities.

Focused etiological hypothesis for cancer in areas where specific Norwegian exposure advantages (natural experiments) exist with collection of sufficient, detailed and validated questionnaire information. Examples; the very restrictive market policy for OCs resulted in a small number of different brands improving the ability to more rigorously define the exact exposure in terms of chemical compounds; diet with focus on the very high fish consumption in parts of Norway including a high dietary intake of fatty acids and D-vitamin; sun bathing habits in a country with large natural differences of UV exposure.

Validated follow-up of cancer, mammograms, causes of deaths and emigrations based on national register linkages using the national birth number.

Repeated collection of exposure information each 5-7 year with complete coverage due to national registers of addresses.